The present invention relates to a data communication system, a relay apparatus, and a portable terminal apparatus in which when a mobile portable terminal apparatus such as a mobile telephone displays a screen based on display screen definition data received from a central apparatus, the exception handling of the data communication can be changed according to the communication environment of the portable terminal apparatus.
With the recent advancement of the computer technology, the communication environment infrastructure has been improving that enables stable mobile communications using mobile units such as mobile telephones and portable terminal apparatuses. Under such an environment, data communication systems where applications the information of which has been conventionally shared in the office can be used outside the office and data communication systems in which such applications can also be used when the mobile unit is moving have been developed in a large number.
For example, when an SFA (Sales Force Automation) application is used with a portable terminal apparatus, the salesperson carrying the portable terminal apparatus establishes communication between the portable terminal apparatus and the SFA server by using a communication protocol such as the HTTP (Hypertext Transfer Protocol), and receives, for example, the display screen definition data from the SFA server, thereby displaying the screen of the desired application on the display of the portable terminal apparatus. The salesperson as the user inputs daily reports, progress reports and the like through the screen displayed on the portable terminal apparatus, transmits them to the SFA server, and stores them into a database or the like of the SFA server.
Under such a mobile communication environment, the established communication can be ceased due to fluctuations in communication traffic or the like. When communication is interrupted in midstream, exception handling is performed such that retry processing is performed a predetermined number of times or that retry processing is performed at predetermined time intervals. Since such exception handling is defined by a service providing program stored in the central apparatus and it is difficult to update the program itself, normally, an exception handling parameter is selected based on the information provided by the user, and the exception handling is performed based on the selected parameter (see Japanese Patent Application Laid-Open No. H04-013332).